For the purpose of hemostasis upon incision of an affected area, blocking the nutrient supply to a tumor, maintaining the concentration of an anticancer drug in a tumor, and the like, a poly(lactic acid/glycolic acid) copolymer (JP 5-969 A), a block copolymer of polyethylene glycol and polylactic acid etc. (JP 5-17245 B, JP 2004-167229 A, JP 2005-312623 A and JP 2007-291323 A), or a multi-block copolymer obtained by copolymerization of lactic acid, polyethylene glycol, polycarboxylic acid and the like (US 2009/0117033 A) is used as polymer particles for embolization of blood vessels and the like.
Such polymer particles for embolization of blood vessels and the like were associated with problems such as inability to achieve rapid biodegradation after having served their purpose. In addition, since these polymer particles, which are used in the form of spherical particles to tightly and securely embolize the blood vessels and the like, are delivered to a target site in a blood vessel or the like through a microcatheter with a small diameter or the like, there were problems such as an occurrence of clogging within the catheter due to insufficient flexibility of the polymer particles or aggregation between the particles, or irreversible deformation of the particles before their reaching to the target site.
To solve these problems, attempts to control the flexibility of polymer particles have been made, by developing polymer particles formed by blending several types of polymers (JP 2007-146146 A), or by developing chemically cross-linked polymer particles (JP 4655505 B). In addition, attempts such as coating the surface of the polymer particles with polyethylene glycol to prevent aggregation between polymer particles and to thereby improve their ability to pass through a catheter (JP 2007-145826 A) have also been reported.
Further, to prevent adhesion and the like between the damage to the surface of an organ which may occur due to surgery and the surrounding tissue, an in situ gel represented by a gel composed of a copolymer such as poly(ethylene glycol/polylactic acid), and poly glycolic acid and the like (JP 3107514 B), or a gel composed of dextran and poly N-isopropyl acrylamide (JP 2003-252936 A); or a binary gel represented by a gel composed of polyethylene glycol and the like and a polycarboxy polysaccharide (JP 2003-531682 A), a gel composed of 2 types of polyethylene glycols and the like (JP 2002-541923 A), or an ion-crosslinked gel such as carboxy methyl chitosan (JP 7-90041 B), for example, is used as a biodegradable material such as an anti-adhesive material, a wound dressing material, a hemostatic material or a urinary incontinence-preventing material.
A poly(ethylene glycol/propylene glycol) copolymer (WO 96/21056), a poly(lactic acid/dioxanone) copolymer (JP 3483753 B), a poly(ethylene glycol/modified amino acid/unmodified amino acid) copolymer (JP 4735260 B), a poly(lactic acid/depsipeptide/ethylene glycol) copolymer (JP 4734772 B), a porous sheet composed of a poly(lactic acid/ethylene glycol) copolymer (JP 2008-36134 A) or the like is also used as a biodegradable material such as an anti-adhesive material, a wound dressing material, a hemostatic material or a urinary incontinence-preventing material; and attempts to control the biodegradability and flexibility thereof have been made.
However, although improvement techniques such as blending several types of polymers (JP 2007-146146 A), use of chemically cross-linked polymer particles (JP 4655505 B), and coating the surface of polymer particles (JP 2007-145826 A) have served to improve the control of the flexibility of polymer particles or their ability to pass through a catheter, no sufficient improvement has been made regarding the problem of irreversible deformation of polymer particles. Further improvement was needed to provide suitable embolization effect for blood vessels and the like. Specifically, there was a need for the development of an embolization material for blood vessels and the like, such as polymer particles with a high capability to recover their original particle shapes after passing through a catheter (hereinafter referred to as “particle shape recovery rate”).
Further, although improvements have been made in increasing biodegradability or flexibility of materials such as anti-adhesive materials, wound dressing materials, hemostatic materials or urinary incontinence-preventing materials, biodegradable materials composed of binary gels, for example, had a problem that their physical properties might be altered depending upon the environmental factors (such as temperature, humidity, or pH) or their blend ratio at the target site. In addition, since the organ or tissue surface damaged by surgery constantly keeps expanding and contracting, the biodegradable material located thereon may be deformed irreversibly. No sufficient improvements have been made regarding these problems of conventional biodegradable materials, and development of a material such as an anti-adhesive material, a wound dressing material, a hemostatic material or a urinary incontinence-preventing material having stable physical properties and a high shape recovery rate has been demanded.
Accordingly, it could be helpful to provide a biodegradable material having an enhanced shape recovery rate after deformation of the material and an improved flexibility.